The total synthesis of natural materials has become an important subject in various fields such as medicine, agricultural chemicals and perfumes. α-iminoesters are extremely useful as precursors of nitrogen-containing natural compounds such as α-amino acids (J. Am. Chem. Soc., 1989, 111, 2582-2855; J. Org. Chem., 1988, 53, 1298-1307; J. Org. Chem., 1991, 56, 1894-1901) and β-amino alcohols (J. Org. Chem., 1976, 41, 3121-3124; J. Am. Chem. Soc., 1997, 119, 7871-7872), and have attracted much attention. However, the monomer tends to decompose or polymerize at room temperature and is extremely unstable and difficult to handle. For these reasons, α-amino acids had to be prepared just before use, making further progress in their use and development difficult.
The present inventors have previously reported the immobilization of unstable silyl enole ethers on resins and their use in various carbon-carbon bond forming reactions (Tetrahedron Lett., 1996, 37, 2809-2812; Tetrahedron Lett., 1996, 37, 5569-5572; Tetrahedron Lett., 1996, 37, 7783-7736; Tetrahedron Lett., 1997, 38, 4251-4254; Molecules Online, 1998, 2, 35-39; J. Org. Chem. 1998, 63, 4868-4869). If an α-iminoester could be immobilized on a polymer in the same manner, the compound maybe stabilized and its handling and storage may be made easier. However, because α-iminoesters are unstable on their own, as described above, it was difficult to even introduce them to a polymer.
The invention of the present application has been accomplished in view of the aforementioned situations and its object is to provide α-iminoester derivatives that are stable under ordinary conditions and provide a method of synthesizing various α-aminoester derivatives at high yield using them, thereby overcoming the limitations of the prior art.